What does "operating pressure" mean on that valve? I see two pressure ratings, and one of them is 75 PSI and the other is 5 PSI.

So, I was thinking of ways to make APFSDS rounds for air cannons, and I realized that threaded rod is basically pre machined to have sabot interface grooves. I 3D printed some fins and sabots and they seem to be durable enough for a few shots as long as the sabot doesn't instantly hit the ground bef...